There are essentially two ways to get your amp overdriving until it growls like a tiger.
The first is using an amp’s designed-in properties to make the speaker in the cabinet – whether combo (that’s an amp and a speaker in one cabinet) or stand-alone – break up and sound generally gnarly. The other is using an overdrive pedal, which should not be confused with a distortion pedal. More on that later.
Overdriving with amplifiers that have both “gain” and “master volume” settings or “volume” and “master volume” settings is a snap. Turning up the gain or first stage volume setting overdrives the tubes on tube amps. Tubes that use triodes, or three elements, are particularly good at producing warm, even harmonics when they are overdriven. Think Marshalls and similar classic growlers. Many solid-state amps have circuitry that mimics the sound of overdriven tubes in an effort to get the warmest distorted sound possible. Nonetheless, solid-state amps are prone to clipping and blunted harmonics when overdriven – which isn’t a bad thing. There are some cool-sounding solid-state amps out there, and they’re cheaper than tube amps.
Amps that lack a gain or simple volume stage are harder to overdrive at low volume and, indeed, may need to be turned way up until their speakers begin to distort. Roy Buchanan is a good reference point for this, since his nasty tone required ear-splitting volume. Larger, multi-speaker vintage American amps are particularly balky, typically failing to produce anything resembling a warm rumble until they are turned too far up to be practical in a typical cub or studio situation.
On the other hand, small vintage amps have a great distortion pattern as they’re turned up. You couldn’t use one to play Pantera covers, but a five-watt Gibson GA5 will help you sound exactly like Chess Records-era Muddy Waters if volume isn’t an issue.
And consider the humble little Supro Thunderbolts that Jimmy Page used to invoke tonal genius on the first Led Zeppelin album.
If you’ve got an amp with gain, experiment. Start with a low master volume setting and play chords as you take the gain from zero to 10. By blending levels of the gain and the master volume, you can find an overdriven sound in your ears’ comfort zone.
Some amps have on-board distortion circuits. Many of them are modeling amps, in which case you’re likely to have an array of simulated classic tube distortion sounds at your disposal. Some amps also have built-in effects, like distortion and chorus. These rarely sound good.
Which brings us to the overdrive pedal, the most natural way to give your tone some fur from a source other than your amp. Overdrive and distortion pedals are the two most common styles of stomp boxes, but they go about their job differently – although distortion pedals are also overdrive pedals. Pure overdrive pedals are all about giving you more of what you’ve already got, while a distortion or fuzz pedal is going to add its own dirty personality, color and tone.
For example, Stevie Ray Vaughan’s favorite pedal was the classic Tube Screamer, which, strictly speaking, is an overdrive rather than a distortion pedal. His breakout contribution to David Bowie’s hit “Let’s Dance” used this box brilliantly to produce a rich, warm, extremely well rounded and expanded version of his basic guitar sound. Overdrive boxes warm up overtones at low volume and get more snarly and distorted only after their gain knob or the guitar’s volume has been rolled up considerably.
Distortion pedals, however, will produce the same nasty sound at any volume. Some players opt to have one of each on their pedal boards – the overdrive for tonal warmth and the distortion for fuzz, which creates all kinds of possibilities for subtle and not-so-subtle grit.